Hydrogen sources for various energy applications, particularly those for “clean” transportation uses, are under development where electric power is impractical as a substitute for those powered by fossil fuels. There is also a strong desire for a portable power source that can perform better than conventional batteries in current consumer devices. Fuel cells are a potential alternative portable power sources that have generated considerable interest because they can: deliver a relatively high energy density; be rapidly refueled; and be used in an “environmental friendly” manner.
Hydrogen generation is commonly carried out by the water-gas-shift (WGS) reaction where carbon monoxide and water are reacted as in Equation 1.CO+H2O→H2+CO2  (1)The WGS reaction is used extensively for coal gasification and fuel reforming and takes place at temperatures of 200-500° C. over a catalyst comprising iron, chromium, nickel, copper, zinc oxide and others metals or oxides. Low temperature WGS reactions are desired and have been suggested in Khan et al., Angew. Chem. Int. Ed. Engl. 27 (1988) 12, 1735-6, which discloses a liquid phase CO hydration process. The two-step low temperature WGS reaction involves carbon monoxide hydration using a soluble catalyst in an aqueous phase, Equation 2, to form an intermediate that can subsequently generate hydrogen in a second step, Equation 3, using a heterogeneous catalyst.CO+H2O→intermediate  (2)Intermediate→H2+CO2  (3)By employing appropriate catalysts, the net WGS reaction can occur at temperature below 100° C. that results in an energy savings and allows fueling of indirect fuel cells where the intermediate can be an organic liquid. The two step process, Equations 2 and 3, also allows the purification of a CO containing hydrogen source.
Significant research and development has focused on fuel cells powered by organic liquids of low molecular weight, with methanol being the most widely investigated. The power density attained by a methanol fuel cell is about 60 mWcm−2, which is an order of magnitude lower than that attainable in a hydrogen fuel cell. Additionally, the permeability of polymer electrolyte membranes to methanol allows methanol diffusion to the cathode, which significantly reduces the voltage and efficiency of a low temperature fuel cell so constructed.
Although very high power densities can be generated in fuel cells powered by pure hydrogen, hydrogen has disadvantages with regard to the cost for its generation and its ease of storage. For example, the weight of a metal hydrogen storage tank is typically more than 20 times the weight of the compressed hydrogen that it can store. An alternative approach to hydrogen storage is “chemical storage” where hydrogen is generated in-situ from a chemical that is stored at ambient pressure.
Chemical storage can circumvent the difficulties of generating and storing hydrogen by liberating hydrogen from organic liquids such as methanol or formic acid. Hydrogen fuel cells employing this in-situ hydrogen generation are referred to as indirect fuel cells. Although generation of hydrogen from small organic molecules requires additional equipment and imposes several addition steps, progress has been slowed due to the unfortunate requirement of reforming catalysts that function only at very elevated temperatures. Nevertheless, a miniature micro-channel reactor for hydrogen generation from methanol and a miniature steam reformation reactor that operates at 190 to 290° C. have been developed. An additional impediment to the development of such fuel cells is that almost all existing catalysts for such devices generate some carbon monoxide (CO) as a by-product, which can poison the fuel cell when present at even minute levels. Development of catalysts that are not poisoned by CO is not the most attractive alternative for consumer or other portable devices. Rather, a catalyst that does not generate toxic CO is desired. Hence there remains a need for a catalytic material or system that can generate hydrogen from small organic molecules at lower temperatures and ambient pressures without generation of CO for the construction of indirect hydrogen fuel cells that power zero emission vehicles or portable consumer devices.